The present invention relates to an office chair and, in particular, to a chair that can naturally adopt either of two positions, a serious working position and a relaxed reclining position, when a person is seated upon it.
The typical office chair that has long been used is provided with a gas spring and a coil spring as attached energy means on the underside of a seat thereof, and the configuration is such that large inclinations of a back rest are implemented by the gas spring whereas small adjustments of the inclination of the back rest in the final stages are implemented by the coil spring.
However, since a gas spring is used as the reclining mechanism for the seat, the manufacturing costs are inevitably high, and thus it is extremely difficult in the prior art to provide an inexpensive chair, despite all efforts to reduce the costs of other components.
In addition, since adjustment of the seat back reactive force in the prior art makes use of a spring such as a coil spring with a single type of spring characteristic, it is difficult to implement a natural reclining state. In other words, the fault occurs that, just by the person sitting, the seat portion and back rest of the chair recline backwards, making it difficult to achieve a working position, on the other hand, if the reactive force of the coil spring is made stronger, this makes it difficult to recline backwards, and in that state reclining becomes so difficult it is not possible to relax.